The present invention relates to a winding device for winding a measuring tape into its housing by the action of a winding spring.
Measuring tapes made of steel, cloth or plastics are widely used for measuring lengths and distances and they are usually wound manually or automatically into their housings.
A measuring tape usable in a self-winding tape measure has an eaves gutter shape section and has the property of straightening itself when having been drawn out from the housing. The measuring tape may be automatically rewound on a winding reel with a winding spring in a housing. The reel driving spring accumulates its force while the measuring tape is being drawn from the housing, and it automatically rotates the reel by the action of its accumulated force to wind the tape thereon.
In measuring a length or a distance with a self-winding tape measure, a user has to draw a measuring tape from the tape measure housing by a necessary length and fix the tape front end at the position by applying a force overcoming a spring force for rewinding the tape on a reel.
Many types of locking mechanisms have been realized in practical use for fixing a measuring tape stretched out from the tape measure housing, overcoming the winding spring force to reduce time and labor of fixing it by a user.
Among the locking mechanisms of the conventional measuring tape winding devices, the most popular one is of the lever type which actuates a lever by directly or indirectly applying an external force thereto to cause a tape fixing cam or pressing member to press the measuring tape against a part of the tape measure housing.
The above-mentioned conventional mechanism is effective to fix the measuring tape at a desired position but requires the user to operate the locking mechanism after drawing the measuring tape from the housing and to release the locking mechanism before rewinding the tape into the housing.
The above-mentioned locking method operates by pressing a part of the measuring tape by a fixing member against a part of the housing. This provides a problem that the measuring tape may be damaged or its scale may be rubbed off if the tape in its fixed condition is stretched out of the housing, by an accident or mis-operation, without previously releasing the lock. Furthermore, the housing shall have considerably increased size to accommodate the fixing mechanism as compared with a tape measure which has no locking mechanism.
Several kinds of self-locking or self-locking and self-releasing devices have been proposed to solve the above-mentioned problem but any of them still requires the user to release the fixing mechanism from the outside and can not eliminate the danger of damaging the measuring tape and/or other parts of the tape measure by the mis-operation. In addition, the fixing mechanism is complicated in itself with use of a spring and requires mounting in a housing of an increased size.
The Japanese Laid-open Utility Model Publication No. 49-11748 discloses a self-locking and self-releasing device for use in a tape measure, which is capable of automatically fixing and releasing a measuring tape and is simple in construction and can be mounted in a tape measure which is similar in size to the conventional unlock-type tape measure. This device, however, has an orientation of its operation. The tape lock can be automatically actuated and released only when the tape measure housing is set in a given direction. This limitation may still cause mis-operation of the device when drawing-out or rewinding the measuring tape and, therefore, can not realize fast and reliable measurement with the tape measure.